Transportation vehicles and methods

ABSTRACT

There is provided, in a preferred embodiment, a transportation vehicle for transporting an individual over ground having a surface that may be irregular. This embodiment has a support for supporting the subject. A ground-contacting module, movably attached to the support, serves to suspend the subject in the support over the surface. The orientation of the ground-contacting module defines fore-aft and lateral planes intersecting one another at a vertical. The support and the ground-contacting module are components of an assembly. A motorized drive, mounted to the assembly and coupled to the ground-contacting module, causes locomotion of the assembly and the subject therewith over the surface. Finally, the embodiment has a control loop, in which the motorized drive is included, for dynamically enhancing stability in the fore-aft plane by operation of the motorized drive in connection with the ground-contacting module. The ground contacting module may be realized as a pair of ground-contacting members, laterally disposed with respect to one another. The ground-contacting members may be wheels. Alternatively, each ground-contacting member may include a duster of wheels. In another embodiment, each ground-contacting member includes a pair of axially adjacent and rotatably mounted arcuate element pairs. Related methods are also provided.

This application is a continuation in part of U.S. application Ser. No.08/250,693, filed May 27, 1994, now U.S. Pat. No. 5,701,965 which inturn is a continuation in part of U.S. application Ser. No. 08/021,789,filed Feb. 24, 1993 now abandoned. These related applications are herebyincorporated herein by reference.

TECHNICAL FIELD

The present invention pertains to vehicles and methods for transportingindividuals, and more particularly to vehicles and methods fortransporting individuals over ground having a surface that may beirregular.

BACKGROUND ART

A wide range of vehicles and methods are known for transporting humansubjects. The design of these vehicles has generally resulted from acompromise that favors stability over maneuverability. It becomesdifficult, for example, to provide a self-propelled user-guidablevehicle for transporting persons over ground having a surface that maybe irregular, while still permitting convenient locomotion over groundhaving a surface that is relatively flat. Vehicles that achievelocomotion over irregular surfaces tend to be complex, heavy, anddifficult for ordinary locomotion.

SUMMARY OF THE INVENTION

The invention provides, in a preferred embodiment, a vehicle fortransporting a human subject over ground having a surface that may beirregular. This embodiment has a support for supporting the subject. Aground-contacting module, movably attached to the support, serves tosuspend the subject in the support over the surface. The orientation ofthe ground-contacting module defines fore-aft and lateral planesintersecting one another at a vertical. The support and theground-contacting module are components of an assembly. A motorizeddrive, mounted to the assembly and coupled to the ground-contactingmodule, causes locomotion of the assembly and the subject therewith overthe surface. Finally, the embodiment has a control loop, in which themotorized drive is included, for dynamically enhancing stability in thefore-aft plane by operation of the motorized drive in connection withthe ground-contacting module.

In a further embodiment, the ground contacting module is realized as apair of ground-contacting members, laterally disposed with respect toone another. The ground-contacting members may be wheels. Alternatively,each ground-contacting member may include a cluster of wheels, eachduster being rotatably mounted on and motor-driven about a commonlaterally disposed central axis; each of the wheels in each cluster maybe rotatably mounted about an axis parallel to the central axis so thatthe distance from the central axis through a diameter of each wheel isapproximately the same for each of the wheels in the cluster. The wheelsare motor-driven independently of the cluster.

In yet another embodiment, each ground-contacting member includes a pairof axially adjacent and rotatably mounted arcuate element pairs. Thearcuate elements of each element pair are disposed transversely atopposing ends of a support strut that is rotatably mounted at itsmidpoint. Each support strut is motor-driven.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood by reference to thefollowing description, taken with the accompanying drawings, in which:

FIG. 1 is a perspective view of a simplified embodiment of the presentinvention, showing a subject seated thereon;

FIG. 2 another perspective view of the embodiment of FIG. 1, showingfurther details of the embodiment;

FIG. 3 is a schematic view of the embodiment of FIG. 1, showing theswivel arrangement of this embodiment;

FIG. 4 is a side elevation of the embodiment of FIG. 1 as used forclimbing stairs;

FIG. 5 is a block diagram showing generally the nature of power andcontrol with the embodiment of FIG. 1;

FIG. 6 illustrates the control strategy for a simplified version of FIG.1 to achieve balance using wheel torque;

FIG. 7 illustrates diagrammatically the operation of joystick control ofthe wheels of the embodiments of FIG. 1;

FIG. 8 illustrates the procedures utilized by the embodiment of FIG. 1to ascend and descend stairs;

FIGS. 9-21 illustrate embodiments of the invention utilizing a pair ofwheel clusters as the ground-contacting members;

FIGS. 9-10 show use of a two-wheel cluster design in various positions;

FIGS. 11-21 show use of a three-wheel cluster design in variouspositions and configurations;

FIGS. 22-24 illustrate an embodiment wherein each ground-contactingmember is realized as a plurality of axially adjacent and rotatablymounted arcuate element groups;

FIGS. 25-26 provide mechanical detail of a three-wheel cluster designfor use in the embodiment of FIGS. 18-20;

FIG. 27 is a block diagram showing communication among the controlassemblies used in the embodiment of FIGS. 18-20;

FIG. 28 is a block diagram showing the structure of a generic controlassembly of the type used in the embodiment of FIG. 27;

FIG. 29 is a block diagram providing detail of the driver interfaceassembly 273 of FIG. 27;

FIG. 30 is a logical flow diagram followed by the central microcontroller board 272 of FIG. 27 in the course of one control cycle;

FIG. 31 illustrates variables defining the dimensions of the clusterdesign of FIGS. 11-26 and of a hypothetical stair with respect to whichthe cluster design will be used for ascent or descent;

FIG. 32 illustrates angle variables pertinent to defining orientation ofthe cluster in relation to the vehicle and to the world;

FIG. 33 is a schematic of the wheel motor control during balancing andnormal locomotion;

FIG. 34 is a schematic of the cluster control arrangement duringbalancing and normal locomotion;

FIG. 35 is a schematic, relating to FIG. 33, showing the arrangement bywhich the state variables indicating wheel position are determined so asto compensate for the effects of cluster rotation;

FIGS. 36-38 illustrate the control arrangement for stair-climbing andobstacle traversal achieved by the cluster design of FIGS. 11-26 inaccordance with a first embodiment permitting climbing;

FIG. 36 is a schematic for the control arrangement for the clustermotors in the first embodiment permitting climbing, here employing alean mode;

FIG. 37 is a schematic for the control arrangement for the wheel motorsin the first embodiment permitting climbing;

FIG. 38 is a block diagram of the state of the vehicle, utilizing thefirst embodiment permitting climbing, for moving among idle, lean, andbalance modes;

FIGS. 39A-B, 40A-B, 41A-B, and 42A-C illustrate stair-climbing achievedby the cluster design of FIGS. 11-26 in accordance a second embodimentpermitting climbing;

FIGS. 39A and 39B illustrate orientation of the cluster in the sequenceof starting stair climbing in accordance with the second climbingembodiment;

FIGS. 40A and 40B illustrate orientation of the cluster in the sequenceof resetting the angle origins in this embodiment;

FIGS. 41A and 41B illustrate orientation of the cluster in the sequenceof transferring weight in this embodiment;

FIGS. 42A, 42B, and 42C illustrate orientation of the cluster in thesequence of climbing in this embodiment;

FIG. 43 is a schematic for the control arrangement for the wheel andcluster motors during the start sequence of FIGS. 39A and 39B;

FIG. 44 is a schematic for the control arrangement for the wheel motorsduring the weight transfer sequence of FIGS. 41A and 41B; and

FIG. 45 is a schematic for the control arrangement during the climbsequence of FIGS. 42A, 42B, and 42C.

FIGS. 46 and 47 show schematically a vehicle in accordance with anembodiment of the present invention equipped with sensors for ascent anddescent of stairs and other similar obstacles.

FIG. 48 shows a vertical section of an embodiment of the invention in aconfiguration, similar that of FIGS. 9-12, utilizing harmonic drives.

FIG. 49 shows detail of the cluster portion of the vehicle of FIG. 48.

FIG. 50 shows detail of the cluster drive arrangement of the vehicle ofFIG. 48.

FIG. 51 shows an end view of a cluster of the vehicle of FIG. 48.

FIG. 52 shows the mechanical details of the hip and knee joints of thevehicle of FIG. 48.

FIG. 53 illustrates an embodiment of the invention providing non-visualoutputs useful for a subject in control of a vehicle.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

The invention may be implemented in a wide range of embodiments. Acharacteristic of many of these embodiments is the use of a pair oflaterally disposed ground-contacting members to suspend the subject overthe surface with respect to which the subject is being transported. Theground-contacting members are motor-driven. In many embodiments, theconfiguration in which the subject is suspended during locomotion lacksinherent stability at least a portion of the time with respect to avertical in the fore-aft plane but is relatively stable with respect toa vertical in the lateral plane. Fore-aft stability is achieved byproviding a control loop, in which the motor is included, for operationof the motor in connection with the ground-contacting members. Asdescribed below, the pair of ground-contacting members may, for example,be a pair of wheels or a pair of wheel clusters. In the case of wheelclusters, each cluster may include a plurality of wheels. Eachground-contacting member, however, may instead be a plurality (typicallya pair) of axially-adjacent, radially supported and rotatably mountedarcuate elements. In these embodiments, the ground-contacting membersare driven by the motorized drive in the control loop in such a way asto maintain the center of mass of the vehicle above the point of contactof the ground-contacting members with the ground, regardless ofdisturbances and forces operative on the vehicle.

In FIG. 1 is shown a simplified embodiment of the invention in which theprincipal ground-contacting members are a pair of wheels and in whichsupplemental ground-contacting members are used in stair climbing anddescending. (As will be shown below, stair climbing and descent andflat-terrain locomotion may both be achieved with a single set ofground-contacting members, when such members are the wheel dusters orthe arcuate elements referred to above.)

The embodiment shown in FIG. 1 includes a support arrangement 12,embodied here as a chair, on which a subject 13 may be seated. Thevehicle is provided with a pair of wheels 11 disposed laterally withrespect to one another. The wheels help to define a series of axesincluding the vertical axis Z--Z, a lateral axis Y--Y parallel to theaxis of the wheels, and a fore-aft axis X--X perpendicular to the wheelaxis. The plane defined by the vertical axis Z--Z and the lateral axisY--Y will sometimes be referred to as the "lateral plane", and the planedefined by the fore-aft axis X--X and the vertical axis Z--Z willsometimes be referred to as the "fore-aft plane". Directions parallel tothe axes X--X and Y--Y are called the fore-aft and lateral directionsrespectively. It can be seen that the vehicle, when relying on the pairof wheels 11 for contacting the ground, is inherently unstable withrespect to a vertical in the fore-aft direction, but is relativelystable with respect to a vertical in the lateral direction.

In FIG. 2 it can be seen that in addition to wheels 11, the vehicle isprovided with a pair of laterally disposed feet 21 capable of beingextended in the vertical direction by controllable amounts, and afootrest 22. The footrests are here provided with sensors fordetermining the height of objects such as stairs over which they may bedisposed. The feet 21 are disposed on a pair of corresponding extendablelegs 23. In a preferred embodiment, the vehicle is stable in thefore-aft direction as well as the lateral direction when both feet arein contact with the ground, but lateral stability may be sacrificed whenone foot is in contact with the ground.

In FIG. 3 is shown an arrangement of the embodiment of of FIGS. 1 and 2permitting swivel of the chair 12 with respect to the suspension system,including feet 21 and related legs 23. The swivel operates in a planethat is approximately horizontal. The swivel arrangement, in combinationwith the ability to extend and retract each leg, permits motion of thevehicle up and down stairs in a manner analogous to human locomotion onstairs. Each leg 23, when serving as the weight-bearing leg, permitsrotation of the remainder of the vehicle about the leg's vertical axisin the course of a swivel. In achieving the swivel, the chair pivotsabout a vertical axis disposed centrally between the legs 23 to maintainthe chair's forward-facing direction. Additionally, thenon-weight-bearing leg 23 is rotated about its vertical axis in thecourse of a swivel to maintain its related foot 21 in a forward-facingdirection.

It can be seen that the embodiment described in FIGS. 1-3 sacrificesinherent fore-aft stability in order to achieve relative mobility. Forgenerally gradual surface changes, the balance mode involves providingfore-aft stability to an otherwise inherently unstable system. For moreirregular surfaces, such as stairs, this embodiment has a separate "stepmode" used for climbing or descending stairs. Stability may be regainedin climbing or descending stairs, for example, by using a hand to graban ordinary handrail 41, as shown in FIG. 4, or even contacting anavailable wall near the stairs.

In addition, a variety of strategies may be used to reduce the risk ofinjury arising from a fall. In one arrangement, in the event that a fallis determined to be about to occur, the vehicle may enter a squat modein which it controllably and quickly lowers the center of mass of thecombination of vehicle and human subject. A lowering of the center ofmass may be achieved, for example, by hinging or separating thesuspension system in such a manner as to cause the height of the chairfrom the surface to be reduced. A squat mode could also have thebeneficial effects of dissipating energy before imparting it to thesubject, placing the subject in a position so as to reduce the subject'svulnerability, and putting the subject in a position that is lower so asto reduce the energy transferred to the person in case of impact.

In the block diagram of FIG. 5 it can be seen that a control system 51is used to control the motor drives and actuators of the embodiment ofFIGS. 1-4 to achieve locomotion and balance. These include motor drives531 and 532 for left and right wheels respectively, actuators 541 and542 for left and right legs respectively, and swivel motor drive 55. Thecontrol system has data inputs including user interface 561, pitchsensor 562 for sensing fore-aft pitch, wheel rotation sensors 563,actuator height sensor 564, swivel sensor 565, and stair dimensionsensor 566.

A simplified control algorithm for achieving balance in the embodimentof the invention according to FIG. 1 when the wheels are active forlocomotion is shown in the block diagram of FIG. 6. The plant 61 isequivalent to the equations of motion of a system with a groundcontacting module driven by a single motor, before the control loop isapplied. T identifies the wheel torque. The character θ identifies thefore-aft inclination (the pitch angle of the vehicle with respect togravity, i.e., the vertical), X identifies the fore-aft displacementalong the surface relative to the reference point, and the dot over acharacter denotes a variable differentiated with respect to time. Theremaining portion of the figure is the control used to achieve balance.The boxes 62 and 63 indicate differentiation. To achieve dynamic controlto insure stability of the system, and to keep the system in theneighborhood of a reference point on the surface, the wheel torque T inthis embodiment is set to satisfy the following equation:

    T=K.sub.1 θ+K.sub.2 θ+K.sub.3 X+K.sub.4 x

The gains K₁, K₂, K₃, and K₄ are dependent upon the physical parametersof the system and other effects such as gravity. The simplified controlalgorithm of FIG. 6 maintains balance and also proximity to thereference point on the surface in the presence of disturbances such aschanges to the system's center of mass with respect to the referencepoint on the surface due to body motion of the subject or contact withother persons or objects.

In order to accommodate two wheels instead of the one-wheel systemillustrated in FIG. 6, the torque desired from the left motor and thetorque desired from the right motor can be calculated separately in thegeneral manner described below in connection with FIG. 33. Additionally,tracking both the left wheel motion and the right wheel motion permitsadjustments to be made to prevent unwanted turning of the vehicle and toaccount for performance variations between the two drive motors.

A manual interface such as a joystick is used to adjust the torques ofeach motor. The joystick has axes indicated in FIG. 7. In operation ofthis embodiment, forward motions of the joystick is used to causeforward motion of the vehicle, and reverse motion of the joystick causesbackward motion of the vehicle. A left turn similarly is accomplished byleftward motion of the joystick. For a right turn, the joystick is movedto the right. The configuration used here permits the vehicle to turn inplace when the joystick is moved to the left or to the right. Withrespect to forward and reverse motion an alternative to the joystick issimply leaning forward or backward, since the pitch sensor (measuring θ)would identify a pitch change that the system would try to compensatefor, leading to forward or reverse motion, depending on the direction oflean. Alternatively, control strategies based on fuzzy logic can beimplemented.

It can be seen that the approach of adjusting motor torques when in thebalance mode permits fore-aft stability to be achieved without thenecessity of additional stabilizing wheels or struts (although such aidsto stability may also be provided). In other words, stability isachieved dynamically, by motion of the components of the vehicle (inthis case constituting the entire vehicle) relative to the ground.

Stair-Climbing with Legs

FIG. 8 shows one manner of stair climbing and stair descending with theembodiment of FIG. 1. In confronting a stair, initially both legs areretracted (shown in block 71), and then the height of the first step ismeasured (block 72). A determination is made whether stair ascent ordescent is to occur (73). (At this point, it is helpful, to achievestability, for the subject to hold an available handrail.)

Thereafter, in the first stage of stair ascent (shown in block 74), afirst leg is extended until the second leg clears the step (75). Thevehicle then swivels until the second leg is over the step it has justcleared (78). (In implementing this stage, it is possible to use asensor to determine how far to swivel based on the step depth.Alternatively, the swivel can be over a specified angle, such as 90degrees.) The sensor is then checked to measure the height of the nextstep (72). If a step is determined to be present (73), and the previousstep was odd (76), the process is continued by extending the second legand retracting the first leg until the first leg clears the next step(79). Next, the vehicle swivels until the first leg is over the clearedstep (80). The sensor is then checked to measure the height of the nextstep (72). If a step is determined to be present (73), and the previousstep was even (76), the process is continued by extending the first legand retracting the second leg until the second leg clears the next step(78). The process is repeated beginning at block 72. If no step isdetected, if the previous step was odd, it is completed by slightlyextending the second leg, fully retracting the first leg, swivelinguntil both legs face forward, and then retracting the second leg tostand on both feet. If no step is detected, if the previous step waseven, it is completed by slightly extending the first leg, fullyretracting the second leg, swiveling until both legs face forward, andthen retracting the first leg to stand on both feet (88).

An analogous procedure is followed for descending stairs. In the firststage of stair descent (shown in block 81), the first leg is slightlyextended to clear the second leg (block 82). Thereafter, the vehicleswivels until the second leg is over the step onto which it is going todescend (84), the first leg is retracted and the second leg is extendeduntil the second leg is on the step (85). The sensor is then checked tomeasure the height of the next step (72). If a step is determined to bepresent (73), and the previous step was odd, the process is continued byswiveling until the first leg is over the step onto which it is going toextend (86). The second leg is then retracted and the first leg extendeduntil the first leg is on the step (block 87). The sensor is thenchecked to measure the height of the next step (72). If a step isdetermined to be present (73), and the previous step was even, theprocess is continued (84), and then repeated beginning at block 72. Ifno step is detected, descent is completed by swiveling until both legsface forward, and then retracting both legs to stand on both feet (88).

In lieu of the swivel arrangement discussed above, in a furtherembodiment, relative motion of the legs may be achieved by causing eachleg to be mounted in a manner as to permit it to slide in anapproximately horizontal plane in the fore and aft directions.Alternatively, the legs may utilize joints analogous to knee and hipjoints of human subjects.

Stair-Climbing with Clusters

Whereas the embodiment of FIG. 1 requires different ground-contactingmembers for stair-climbing and for level terrain navigation, theembodiments of the invention shown in FIGS. 9-21 successfully utilizethe same set of ground-contacting members for both stair-climbing andfor level terrain navigation. FIGS. 9-18 illustrate embodiments of theinvention utilizing a pair of wheel clusters as the ground-contactingmembers in lieu of the pair of wheels used in the embodiment of FIG. 1.

In FIG. 9, there is shown a side view of an embodiment utilizing atwo-wheel cluster design. The subject 962 is shown supported on the seat95 of this embodiment. In view is the right-hand cluster 91 with a pairof wheels 931 and 932 in radially symmetric locations about thecluster's axis 92 of rotation. A similar left-hand cluster is alsoemployed. Each cluster has its own separately controlled motor to driveit about its axis of rotation 92. Each pair of wheels (here, 931 and932) is also driven by a separately controlled motor about its own axisof rotation, but the wheels of a cluster are coupled to rotatesynchronously.

It can be seen in FIG. 9 that the cluster 91 is positioned so that bothwheels 931 and 932 may be in contact with the ground. When the cluster91 (along with the left-hand cluster) is in this position, the vehicleof this embodiment is relatively stable in the fore-aft plane, therebypermitting a subject 961 shown standing) to assume rapidly a comfortableseated position 962 on the vehicle or, for example, a handicapped personto transfer from another chair.

The cluster 91, however, may be rotated about its axis 92 until onlywheel 932 of each duster is in contact with the ground as shown in FIG.10. When the cluster 91 (along with the left-hand cluster) is in thisposition, the vehicle has the same inherent fore-aft instability asdiscussed above in connection with the embodiment of FIG. 1. The sameequations governing the system may be used as discussed above in orderto drive the wheels to create fore-aft stability dynamically. Also asshown in FIGS. 9 and 10, the chair 95 may be linked to theground-contacting members via an articulated arm having segments 941 and942 that may be adjusted in angle with respect to each other and theseat 95. The adjustments are achieved by motorized drives disposed athubs 945 and 946. (Such drives may, for example, be harmonic drives.) Asa result of these adjustments (in addition to the effect of rotating theclusters), the height of the seat 95, among other things, may bechanged; it can be seen that the subject 101 may achieve a height whileseated on the vehicle comparable to (or even greater than) a standingsubject 961. This is desirable, since seated subjects, in wheel chairs,for example, are commonly dwarfed by standing subjects. As will bediscussed in further detail below, the foregoing adjustments also permitadjustment of the fore-aft tilt of the seat.

FIGS. 11-18 show use of a three-wheel cluster design in various modesand configurations. FIGS. 11 (showing stable rest position) and 12(showing balancing position for travel) for three-wheel clusterscorrespond to FIGS. 9 and 10 for two-wheel clusters. Each three-wheelcluster (right-hand cluster 111 is shown here) is rotatably mounted andmotor-driven about axis 112, using separately controllable motors. As inthe case of the two-wheel cluster design, the wheels of each cluster areseparately driven and controlled, but run synchronously in each cluster.

It should be noted that although many of the embodiments describedherein utilize separate motors individually controlled, a common motormay be used for a number of functions, and the separate control may beachieved by appropriate clutch or other power transmission arrangement,such as a differential drive. The term "motorized drive" as used in thisdescription and the following claims means any vehicle that producesmechanical power regardless of means, and therefore includes a motorthat is electric, hydraulic, pneumatic, or thermodynamic (the latterincluding an internal combustion or an external combustion engine)together with any appropriate arrangement for transmission of suchmechanical power; or a thrust-producing device such as a turbojet engineor a motor-driven propeller.

FIG. 13 is similar to FIG. 12, but here the chair 95 is shown having aback 131 and a seat 132. The angle of back 131 relative to the seat 132and the angle of the seat 132 relative to the horizontal may be adjustedso that with the back 131 in a generally vertical orientation, the seat132 may be tilted toward the vertical to permit the user to assume amore nearly standing position.

In FIG. 14, the embodiment is shown climbing stairs. The articulated armsegments 941 and 942 are here in the extended position to providemaximum height, so that the feet of the subject 101 to clear the stairs141. Stair climbing is achieved by rotation of each of the right cluster111 and left cluster (not shown) about central axis 112 and coordinatedrotation of the wheels. The actual modes and control arrangements forachieving stair climbing are described below in connection with FIG. 27et seq.

FIGS. 15-17 are views of an embodiment similar to that of FIGS. 11 and12, but in which one of the segments 161 and 171 of the articulated arm,in this case segment 171, actually carries seat 151 of the body supportcombination comprising seat 151 and surround 152. Surround 152 is hereprovided with headrest 155. When the segment 171 is oriented in anear-vertical position, the seat 151 moves out of the way, permittingthe subject 153 to assume a standing position supported by seat 151,surround 152, and footrest 154.

FIGS. 18-20 illustrate an embodiment, similar to that of FIGS. 11-14, inwhich the height of subject 101 can be adjusted by telescoping member181, the extension of which is under separate motor control. Inaddition, the roll angle of the subject, about an axis R--R in FIG. 19,is adjustable as shown in FIG. 18, via separately controlled motor unit191 of FIG. 19. Furthermore, the fore-aft tilt of chair 181, shown intwo different positions in FIGS. 19 and 20, is adjustable via separatelycontrolled motor unit 192. Although the roll and tilt adjustments arehere implemented with a pivot and a motorized drive, each of theseadjustments could also be implemented, for example, by a four-bar orother linkage arrangement coupled to a motorized drive.

In FIG. 21, it can be seen that a vehicle can be made in accordance withthe present invention without providing a chair. The subject stands on aplatform 211 and holds a grip 212 on handle 213 attached to the platform211, so that the vehicle of this embodiment may be operated in a manneranalogous to a scooter. The grip 212 may be conveniently provided with athumb-operated joystick for directional control, although other methodsof control may also be used. For example, the handle 213 and grip 212may be avoided altogether, and the platform 211 may be equipped withsensors to detect leaning of the subject. Indeed, as described inconnection with FIG. 5 and as further described below, the pitch of thevehicle is sensed and compensated for in the control loop, so that ifthe subject leans forward, the vehicle will move forward to maintainvertical stability. Accordingly, a forward lean will cause forwardmovement; a backward lean will cause backward movement. Appropriateforce transducers may be provided to sense leftward and rightwardleaning and related controls provided to cause left and right turning asa result of the sensed leaning. The leaning may also be detected usingproximity sensors. Similarly, the vehicle of this embodiment may beequipped with a foot- (or force-) actuated switch to activate thevehicle, in such a manner that the switch is closed so as to power thevehicle automatically when the subject stands on the platform 211.Although this embodiment is shown with left and right wheel clusters 214operated in the manner of the clusters of FIGS. 13-20, the vehicle maybe alternatively provided with other ground-contacting members, such aswith a transversely disposed single pair of wheels in the manner of FIG.1 (but without legs) or with left and right pairs of axially adjacentand rotatably mounted arcuate element pairs in a fashion similar to thatof FIGS. 22-24 described below.

Stair-Climbing Using Arcuate Elements

FIGS. 22-24 illustrate an embodiment wherein each ground-contactingmember is realized as a plurality (here a pair) of axially adjacent,rotatably mounted arcuate element groups. For example, in FIG. 22, whichcorresponds generally to the cluster-propelled embodiment of FIG. 15,the right-hand ground-contacting member is realized as arcuate pair 221and 222. The arcuate elements (items 221a-221b and items 222a-222b) ofeach pair 221 and 222 are transversely disposed at opposing ends of asupport strut (items 221c and 222c respectively) that is rotatablymounted at its midpoint. Each support strut 221c and 222c is motordriven and is controllable independently of the other. In operation,during normal locomotion, the arcuate elements of each pair approximateaction of a wheel. When, for example, during such locomotion, arcuateelement 221a is about to lose contact with the ground, element 222a hasbeen rotated so as to arrive at the position shown to permit the rollestablished by the shape of the arcuate elements to continue. In thisfashion, there is a substantially continuous rolling motion of thevehicle along the arcuate elements. Thus the motion of each of thearcuate elements about its axis of rotation is not generally at constantangular velocity. Typically each arcuate element pair moves at a greaterangular rate when neither element of the pair is in contact with theground. However, when one element of the pair is in contact with theground, the angular velocity of the pair (and therefore of theground-contacting element) is controlled to match the desired groundvelocity of the vehicle, so that constant ground velocity can beachieved when desired.

An effect resulting from changes in angular velocity of the arcuateelements to permit constant ground velocity is the presence of areactive torque on the frame that would tend to cause undesired vehicleaccelerations. One solution is to design the vehicle so that thereactive torque of the motor drive is equal and opposite to the reactiveof the arcuate element it drives, expressed as follows:

    I.sub.R ω.sub.R +I.sub.L ω.sub.L =0,

where I is the moment of inertia, and subscript L denotes the arcuateelement system and subscript R denotes the rotor system. This equationcan be rewritten as ##EQU1## The gear ratios N_(g) may be substitutedfor the ratio of the angular accelerations, as follows: ##EQU2## Bysatisfying this equation for N_(g), which can be accomplished bysuitable configuration of the gear ratio and the inertias, the reactivetorques will be in balance and the vehicle will proceed smoothly.

Preferably the radially outermost extent of each arcuate element has agenerally constant main radius of curvature that conforms generally withthat of a circle having a radius of length equal to the distance of thatextent. Each arcuate element has a leading portion, which approaches theground first in forward motion of the vehicle, and a trailing portion,which leaves the ground last in forward motion of the vehicle. Theleading portion of arcuate element 221a, for example, is identified asitem 223 and the trailing portion of arcuate element 221a is identifiedas item 224. To permit successive arcuate elements to contact the groundsmoothly in the course of forward motion, it is preferable that theradius of curvature of each arcuate element near the tip of its leadingportion should be somewhat smaller than such element's main radius ofcurvature. Similarly, to permit successive arcuate elements to contactthe ground smoothly in the course of rearward motion, it is preferablethat the radius of curvature of each arcuate element near the tip of itstrailing portion should be somewhat smaller than such element's mainradius of curvature. Alternatively, or in addition, the radius ofcurvature near the tips of the leading portion and trailing portion mayadjusted in other ways to facilitate the transfer of load from onearcuate member of the group to the next. It may be desirable, forexample, in some embodiments to cause the tip radius of curvature to begreater than the main radius of curvature. In other embodiments, the tipmay be deflectably mounted and is coupled to a deflection arrangement,so that on actuation the local radius of curvature may be modified.

It should be noted that, when desired, the vehicle of this embodimentmay be placed in a rest position, by scissoring struts 221c and 222c tosuch an angle (approaching π radians) that the leading portion of onearcuate element is in contact with the ground, the trailing portion ofanother arcuate element is in contact with the ground, and the points ofcontact are spaced apart from one another. Such a position also reducesthe overall height of the vehicle and facilitates compact storage ortransport of the vehicle.

In FIG. 23, which corresponds generally to the cluster-propelledembodiment of FIG. 17, the vehicle of FIG. 22 is shown with the subjectstanding on platform 154 with the seat 151 oriented vertically.

In FIG. 24, the embodiment of FIG. 22 is shown climbing stairs. Thestruts are moved in such a way that successive arcuate elements land onsuccessive stairs.

Details of Cluster Implementation

FIGS. 25-26 provide detail of a three-wheel cluster design for theembodiment of FIGS. 18-20. Each cluster 251a and 251b has its own drivemotor 252a and 252b, which drives the cluster through a gear train. Thewheels of each cluster are powered separately by a motor 253a forcluster 251a and by a motor 253b for cluster 251b. The wheels within agiven cluster 251a or 251b are driven synchronously by such cluster'smotor 253a or 253b, as the case may be, through a radially disposed geararrangement. A side view of the cluster 251a in FIG. 26 shows wheels261a, 261b, and 261c with associated drive gears 262a, 262b, and 262c,driven by respective idler gears 263a, 263b, and 263c, which in turn aredriven by power gear 264, which is turned by the shaft of motor 253a.

FIG. 27 is a block diagram showing communication among the controlassemblies used in a vehicle according to the embodiment of FIGS. 18-20.A similar set of assemblies may be used for any of the other embodimentsdescribed herein. The vehicle is powered by battery stack 271. Bus 279provides communications (here implemented serially) among and power tothe various assemblies. Overall system control of the vehicle isprovided by central micro controller board 272. Inputs, derived fromsources such as the joystick and inclinometer, to the central microcontroller board 272 that establish the basis for system control areprovided by the driver interface assembly 273, which is described belowin connection with FIG. 29. The tilt, height, and roll of the chair 182of FIG. 18 are adjusted by tilt motor control assembly 274, height motorcontrol assembly 275, and roll motor control assembly 276 respectively.Rotation of the right and left dusters is controlled by right clustercontrol assembly 278a and left cluster control assembly 278brespectively. Rotation of the wheels in the right cluster and in theleft cluster is controlled by right wheel control assembly 277a and leftwheel control assembly 277b.

The general structure of each of the control assemblies, identified inFIG. 27, used for the chair position and wheels and clusters is shown inFIG. 28. A motor 281 receives 3-phase power from power converter 282.Output from Hall effect detector 2812 provides information signals tothe power converter 282 to control the phase of power to the motor.Information signals relating to the shaft rotation of the motor or ofthe position of mechanical systems powered by the motor may be providedby one or more of potentiometer 284, tachometer 2811, or incrementalencoder 2813. (Alternatively, the Hall effect detector 2812 may itselfbe utilized.) These signals are fed to peripheral micro controller board283. Additionally temperature outputs associated with power converter282 and motor 281 provide input signals to the peripheral microcontroller board 283. The peripheral micro controller board 283 is inturn in communication with the central micro controller board 272 overbus 279.

FIG. 29 is a block diagram providing detail of the driver interfaceassembly 273 of FIG. 27. A peripheral microcomputer board 291 receivesan input from joystick 292 as well as from inclinometer 293. Theinclinometer provides information signals as to pitch and pitch rate.(The term "inclinometer" as used in this context throughout thisdescription and in the accompanying claims means any device providing anoutput indicative of pitch or pitch rate, regardless of the arrangementused to achieve the output; if only one of the pitch and pitch ratevariables is provided as an output, the other variable can be obtainedby suitable differentiation or integration with respect to time.) Topermit controlled banking into turns by the vehicle (thereby to increasestability while turning) it is also feasible to utilize a secondinclinometer to provide information as to roll and roll rate or,alternatively, the resultant of system weight and centrifugal force.Other inputs 294 may also be desirably provided as an input to theperipheral micro controller board 291. Such other inputs may includesignals gated by switches (knobs and buttons) for chair adjustment andfor determining the mode of operation (such as lean mode or balance modedescribed below). The peripheral micro controller board 291 also hasinputs for receiving signals from the battery stack 271 as to batteryvoltage, battery current, and battery temperature. The peripheral microcontroller board 291 is in communication over bus 279 with the centralmicro controller board 272.

FIG. 30 is a logical flow diagram followed by the central microcontroller board 272 of FIG. 27 in the course of one control cycle. Fordiagnostic purposes, the cycle begins at step 301, checking for thepresence of any input from the technician. The next step, 302, is toread the driver's inputs from the joystick, switches, knobs, andbuttons. Next, in step 303, the state variables of the vehicle are readas inputs. Next, in step 3011, the technician's display is updated (incase of diagnostic use), and then, in step 304, the program state ismodified based upon the input variables obtained in steps 301 through303. A test is then made whether to exit the program (step 3041), and ifthe determination is yes, all of the motor amplifiers are disabled (step3042), and the program is ended. Otherwise, a safety check is made (instep 3043) of pertinent variables (such as temperature, battery voltage,etc., and if the result is negative, the wheel and cluster motoramplifiers are disabled (step 3044), and the program state is thenmodified (step 3055). However, several levels of checking are suitablyemployed so that the motor amplifiers are disabled only after thresholdalarm conditioners have been established. If the safety check in step3043 is positive or after the program state is modified in step 3055,calculations are performed seriatim for the cluster torque signal (step305), wheel torque signal (step 306), tilt velocity signal (step 307),roll velocity signal (step 308), and height velocity signal (309). Theresults of these calculations are then provided as an output to theirrespective vehicles in step 3010. Under step 3091, the program waits forthe next timing signal to begin the control cycle again. The frequencyof the control cycles in this embodiment is in the range of 200-400 Hz.,which provides satisfactory control responsiveness and stability.

FIG. 31 illustrates variables defining the dimensions of the clusterdesign of FIGS. 11-26 and of a hypothetical stair with respect to whichthe duster design can be used for ascent or descent. Set forth in thefollowing table are variables used to identify these dimensions shown inFIG. 31. "Nominal size" means typical dimensions of these items, inconnection with which the embodiment of FIGS. 18-20 has been implementedand functions.

                  TABLE 1                                                         ______________________________________                                        Dimension Variables                                                                                       Nominal                                           Variable  Description       Size                                              ______________________________________                                        L         Distance from cluster center to                                                                 21.0"                                                       center of mass of system                                            l         Distance from cluster center to                                                                 5.581"                                                      wheel center                                                        l'        Distance from wheel center to                                                                   9.667"                                                      wheel center                                                        d         Depth of stair    10.9"                                             h         Height of stair   6.85"                                             z         Distance between the edge of the                                                                3.011"                                                      riser and the wheel contact point                                             when four wheels are in contact                                               with the stairs and the lower                                                 wheels are against the riser. This                                            can be calculated using z = (l'.sup.2 -                                       h.sup.2).sup.1/2  - r.                                              r         Radius of the wheel                                                                             3.81"                                             ______________________________________                                    

The following conventions have been employed in using these variablesand those in Table 2 below in connection with the description below:

1. Variables defined in world coordinates are named using a singlesubscript in capital letters. World coordinates are coordinates fixed tothe earth (inertial).

2. Variables defined in relative coordinates are named with a dualsubscript. The subscripts indicate the endpoints of the variable. Theorder of the subscripts indicates the sign of the variable. For example,θ_(PC) is the angle between the post and the cluster leg where clockwiserotation from the cluster post is positive (see note 4). A cluster's"leg" is the line segment from the center of the cluster to the centerof the wheel that is currently being balanced on. A cluster's "post" isthe line segment from the system's center of mass to the center of thecluster.

3. Lower case subscripts are used to indicate other attributes, e.g.,right/left, etc.: r=right; l=left; ref=reference; f=finish; s=start.

4. All angles are positive in the clockwise direction, where positivetravel is in the positive x direction.

5. A dot over a variable indicates differentiation in time, e.g., θ.

FIG. 32 illustrates angle and motion variables pertinent to definingorientation of the cluster in relation to the vehicle and to the world.These variables are defined as set forth in the following table.

                  TABLE 2                                                         ______________________________________                                        Angle and Motion Variables.                                                   Variable                                                                             Name       Description                                                 ______________________________________                                        θ.sub.c                                                                        Theta Cluster                                                                            The angle between vertical and the line                                       from the wheel that is currently being                                        balanced on to the cluster hub.                             θ.sub.w                                                                        Theta Wheel                                                                              The angle between vertical and an                                             arbitray radial line on the wheel.                          θ.sub.PC                                                                       Theta Post-                                                                              The angle centered at the cluster hub that                         Cluster    starts at the post and ends at the leg being                                  balanced on. (θ.sub.PC = 180° when                               balanced on                                                                   one wheel with the leg vertical.)                           θ.sub.PW                                                                       Theta Post-                                                                              The angle between the post and the                                 Wheel      arbitrar line on the wheel.                                 x      x          The linear position of the wheel center                                       alon the floor in reference coordinates.                    θ.sub.I                                                                        Theta      The angle of the inclinometer with respect                         Inclinometer                                                                             to gravity.                                                 θ                                                                              Theta (Pitch                                                                             The actual angle between center of mass of                         Angle)     the vehicle and the wheel center. This is                                     derived by compensating inclinometer                                          angle θ.sub.I for θ.sub.C and                                     θ.sub.PC.                                             ψ  Yaw Angle  The angle between the X axis of the vehicle                                   and the x-axis of the reference frame.                      ______________________________________                                    

FIGS. 33-35 are block diagrams showing control algorithms, suitable foruse in conjunction with the control assemblies of FIG. 27, to providestability for a vehicle according to the embodiment of FIGS. 11-21 whenbalanced on a pair of wheels, both during locomotion and in a fixedposition.

FIG. 33 shows the control arrangement for the motors of the right andleft wheels (corresponding to items 252a and 252b of FIG. 25). Thearrangement has inputs of θ, θ, rθ_(wl) (linear velocity of the leftwheel relative to the world coordinate system) and rθ_(wr) (linearvelocity of the right wheel), in addition to directional inputs 3300determined by joystick position along X and Y axes of a referencecoordinate system. Inputs θ, θ, and error signals x and x (describedbelow), subject to gains K1, K2, K3, and K4 respectively, become inputsto summer 3319, which produces the basic balancing torque command forthe wheels, in the general manner described above in connection withFIG. 6 above. The output of summer 3319 is combined with the output ofyaw PID loop 3316 (described below) in summer 3320, then divided individer 3322 and limited in saturation limiter 3324, to produce the leftwheel torque command. Similarly, the output of summer 3319 is combinedwith the output of PID loop 3316 in summer 3321, then divided in divider3323 and limited in saturation limiter 3325, to produce the right wheeltorque command.

In FIG. 33, a directional input along the X axis moves the referencecoordinate system along its X axis relative to the world coordinatesystem (which represents the traveled surface), at a velocityproportional to the displacement of the joystick. A directional inputalong the Y axis rotates the reference coordinate system about its Zaxis at an angular velocity proportional to the displacement of thejoystick. It will be appreciated that motion of the joystick in thepositive X direction is here interpreted to mean forward motion; motionof the joystick in the negative X direction means reverse motion.Similarly, motion of the joystick in the positive Y direction meansleftward turning, counter-clockwise as viewed from above; motion of thejoystick in the negative Y direction means rightward turning clockwiseas viewed from above. Hence the directional inputs Y and X are givendeadband via deadband blocks 3301 and 3302 respectively, to widen theneutral position of the joystick, then subject to gains K11 and K10,then rate-limited by limiters 3303 and 3304 respectively, which limitthe angular and linear accelerations respectively of the referencecoordinate system. The sum of these outputs achieved through summer 3305becomes the reference velocity x_(r) ref whereas the difference of theseoutputs achieved through summer 3306 becomes the reference velocityx_(l) ref These reference velocities are subtracted in summers 3308 and3307 from compensated linear velocity input signals rθ_(wl) and rθ_(wr)for left and right wheels (see description below in connection with FIG.35 for these quantities) to obtain velocity error signals x_(l) andx_(r) for left and right wheels within the reference coordinate system.In turn the average of these signals, determined via summer 3317 anddivider 3318, produces a linear velocity error signal x. Displacementerror signal x is derived by integrating rθ_(wl) and rθ_(wr) inintegrators 3310 and 3309, limiting the results in saturation limiters3312 and 3311, and then averaging their outputs via summer 3313 anddivider 3315. The difference between these displacements, determined viasummer 3314, produces the yaw error signal ψ.

The yaw error signal ψ is run through a standardproportional-plus-integral-plus-derivative (PID) control loop 3316, theoutput of which is combined with the output of the basic balancingtorque command of summer 3319, to produce the individual wheel torquecommands, which cause the wheels to maintain fore-aft stability and alsocause the vehicle to align itself with the axes of, and follow theorigin of, the reference coordinate system as directed by directionalinput 3300.

FIG. 34 is a schematic of the cluster control arrangement. Theorientation of the clusters can be controlled by directional inputs3400. If desired, the same joystick as used to provide directionalinputs 3300 to the wheels may be switched, by a separate switch, to beoperative, in a separate mode, to provide the directional inputs 3400specifying the orientation of the clusters. In a fashion generallyanalogous to the signal path through summers 3306 and 3305 of FIG. 33,here the joystick signals resulting from positive displacement in the Xdirection are added, and signals resulting from positive displacement inthe Y direction are subtracted from one another, in summers 3402 and3401 to provide left and right cluster rotation rate signals, which,after integration in integrators 3404 and 3403 respectively, providedesired cluster angle orientation information to left and right dustersummers 3406 and 3405 respectively.

Absent directional inputs 3400, the preferred cluster orientation,normally θ_(PC) ref =π radians, is provided over line 3413 of FIG. 34 toeach of the summers 3406 and 3405, along with signals showing actualduster orientation θ_(PCl) and θ_(PCr) (derived by passing cluster anglerate signals from left and right cluster encoders through integrators3412 and 3411 respectively). The outputs of the summers 3406 and 3405are therefore cluster position error signals for the left and rightclusters respectively. These signals are fed through PID control loops3408 and 3407 and saturation limiters 3410 and 3409 to drive the leftand right cluster motors.

FIG. 35 is a schematic, relating to FIG. 33, showing the arrangement bywhich the state variables indicating wheel position, pitch, and pitchrate are determined so as to compensate for the effects of clusterrotation. As mentioned in Table 2, the pitch angle θ is the actual anglebetween the center of mass of the vehicle and the center of the wheelthat is currently being balanced on. The angle θ_(I) measured by theinclinometer is the angle of the post with respect to the vertical.Hence the actual pitch angle θ is based on θ_(I) from which a correctionsignal θ_(I) corr is subtracted by summer 3518. The signal θ_(I) corr iscalculated in summer 3516 as θ_(PC) +π-θ_(C). The signal θ_(PC) isdetermined as the average of the left and right post-to-cluster anglesθ_(PCl) and θ_(PCr) obtained from integration in integrators 3509 and3510 of left and right cluster encoder outputs; the average is obtainedby using summer 3511 and divider 3512. Assuming that the vehicle isbalanced, θ_(C) can be derived from θ_(PC) using the formula ##EQU3##This calculation is achieved in section 3515. The θ_(Icorr) isdifferentiated by differentiator 3517 to provide a correction to pitchrate signal θ_(I), which is supplied by summer 3519, yielding thecorrected output θ.

Similarly, the linear left and right velocities rθ_(wl) and rθ_(wr) forleft and right wheels are derived from differentiation bydifferentiators 3507 and 3508 of the derived linear left and rightposition signals rθ_(wl) and rθ_(wr). The position signals, in turn, arederived by multiplying by a gain of r in multipliers 3505 and 3504 thedetermined absolute angular positions θ_(Wl) and θ_(Wr) of the left andright wheels. The angular positions θ_(Wl) and θ_(Wr) are determined byfirst integrating the left and right wheel encoder signals θ_(PWl) andθPWr in integrators 3501 and 3502 to obtain θ_(PWl) and θ_(PWr). Thesesignals are then fed into summers 3503 and 3504 where they arecompensated for the effects of cluster rotation by the addition of θ_(C)and the quantity 1/2(θ_(PC) -π) derived from summer 3513 and divider3514.

FIGS. 36 and 37 are block diagrams showing control algorithms, suitablefor use in conjunction with the control assemblies of FIG. 27, to permita vehicle according to the embodiment of FIGS. 11-21 to achievestair-climbing and obstacle traversal in accordance with a firstembodiment permitting climbing. In this embodiment the clusters are putin a lean mode, in which they are rotated to attempt to maintain balancein the same general manner as used in normally balancing by wheelrotation as shown in FIG. 33. The same basic equations are used. In FIG.36, summer 3601 provides correction signals to drive the left and rightclusters, derived, among other things, from inclinometer 3602, whichprovides pitch and pitch rate signals θ and θ via gains K1 and K2respectively. The encoder outputs from left and right clusters provideinputs of θ_(PCl) and θ_(PCr), which are integrated by integrators 3603and 3604 respectively and saturation limited by limiters 3605 and 3606respectively to produce θ_(PCl) and θ_(PCr). These values, when averagedvia summer 3608 and divider 3610, result in angular displacement θ_(PC),which is provided through gain K3 as an additional input to summer 3601.The velocity θ_(PC), determined as the average of θ_(PCl) and θ_(PCr),via summer 3617 and divider 3618, is a further input to summer 3601,this time via gain K4. The output of summer 3601 provides uniform driveof the left and right cluster motors via summers 3611 and 3612, dividers3613 and 3614, and saturation limits 3615 and 3616 respectively. Inaddition, however, the twist signal, via PID control loop 3609, providesa differential drive through summers 3611 and 3612 to the left and rightcluster motors. The twist signal is derived by using summer 3607 tosubtract the signals θ_(PCl) and θ_(PCr) from one another.

When the clusters are in the lean mode, the wheels are in a slave mode,in which the wheels are driven as a function of the rotation of theclusters. This is shown in FIG. 37, where θ_(PC), derived from FIG. 36,as output from divider 3610, is multiplied by a climb ratio constant ingain 3701 to produce θ_(PWref), a signal that is fed to summers 3703 and3702 to control the left and right wheel motors via PID control loops3705 and 3704 and saturation limits 3707 and 3706 respectively. Acomparison of FIGS. 37 and 34 show that the wheels are slaved to theclusters in FIG. 37 in the same manner that the clusters are slaved tothe vertical (π radians) input 3413 in FIG. 34. In FIG. 37, the summers3703 and 3702 have two other inputs each. One input is to track theresults of directional inputs 3714 from the joystick, which, in a manneranalogous to the processing in FIG. 34, via summers 3709 and 3708 andintegrators 3711 and 3710, produces left and right control signalsprovided as inputs summers 3703 and 3702 respectively. Another input isto track the effects of wheel rotation, so θ_(PWl) and θ_(PWr), obtainedby running the left and right wheel encoder outputs through integrators3713 and 3712 are also subtracted by summers 3703 and 3702.

The use of the lean mode provides a powerful and stable method toachieve climbing over obstacles. The climb ratio is determined by themultiplier selected for gain 3701 of FIG. 37. Once this is determined(an item that can be selected manually or automatically determinedfollowing obstacle measurement using appropriate spatial sensors ordetermined in whole or in part empirically based on the state variablesthemselves) the vehicle can surmount obstacles by the subject's leaningor causing the vehicle to lean in the desired direction. The clustersrotate to maintain balance at the same time that they, with the wheels,are rotating over the obstacles. When the vehicle does not encounterobstacles, it may desirably be operated in the balance mode of FIGS. 33and 34, with the clusters slaved to π radians and the wheels maintainingbalance and causing desired locomotion.

The transitions between wheel balancing mode and cluster lean mode are amatter requiring attention. FIG. 38 is a block diagram of the state ofthe vehicle, utilizing the embodiment of FIGS. 33-37, among idle, lean,and balance modes. At key times, there will be no state change until itis determined that (θ_(PC) -π) mod (2π/3)=0. This is a point at whichthe center of mass is approximately above the ground contacting pair,and such a condition is referred to as a "zero crossing" below in thisdescription and in the following claims. At the zero crossing, thecluster is in a position so that, for example, it can be slaved to theθ_(PC) =π position in the manner of FIG. 34. After beginning at block3801, the vehicle's initial state is To Idle 3802, from which it entersand remains in Idle 3803, until the Run/Idle switch is moved into theRun position. Once in that position, the vehicle enters the From Idlestate 3804. Because there is no absolute reference on either of theclusters, we assume that the vehicle is on flat, level ground at state"From Idle" 3804, where an absolute reference is established. Allmovement of the clusters determined by the incremental encoders isrelative to this reference. At this point, or at any later point, if theRun/Idle switch is moved back to the Idle position, the state returnsover path 3812 to the To Idle state 3802. Otherwise, the state becomesWait 3805, and remains there, until it is determined that θ=0, whereuponthe state becomes To Lean 3806. To Lean then moves to Lean 3807, andremains there, unless a switch is moved. If the Lean/Balance switch isthen placed in the Balance position and if the clusters experience azero crossing, then the state moves successively to From Lean 3808, toBalance 3809, and finally to Balance 3810. If the Lean/Balance switch ismoved to the Lean position, the state moves to From Balance 3811 andback to Lean 3806.

The Wait state allows a smooth startup of the wheel and cluster motors.Without it, the control loop would immediately attempt to compensate fora potentially large error signal from the inclinometer. By starting at azero crossing, this is avoided. An additional technique of monitoring θand requiring it to be below a certain threshold at a zero crossingprovides an even softer start.

FIGS. 39A-B, 40A-B, 41A-B, and 42A-C illustrate the sequences in acontrol arrangement, to permit a vehicle according to the embodiment ofFIGS. 11-21 to achieve stair climbing in accordance a second embodiment.Four basic sequences of operation are involved in this embodiment:start; reset angle origins; transfer weight; and climb. This embodiment,among others, may be conveniently implemented in the control arrangementof FIG. 27. Block diagrams showing control algorithms for achievingthese four sequences are shown in FIGS. 43 (start), 44 (transferweight), and 45 (climb). (No motion is involved in the reset angleorigins sequence, so no control algorithm is shown for this sequence.)FIGS. 39A and 39B illustrate orientation of the cluster in the startsequence. In this sequence, the cluster moves from its normal balancingposition on two wheels (FIG. 39A) to a position (shown in FIG. 39B) inwhich a first pair of wheels (one from each cluster) is on a first leveland a second pair of wheels from each cluster is on the next stair. Theangle values used in this description in connection with FIGS. 39Athrough 42C are those resulting from application of the nominal stairand cluster wheel sizes given in Table 1 above. In the start sequence,algorithm shown in FIG. 43, an input is provided of θ_(C) ref as afunction of time to the cluster block 4301; the function varies smoothlyfrom the start to the finishing values. Alternatively, an input ofθ_(PC) ref can be provided in a similar fashion. Here the input of θ_(C)ref is run through processor 4302 to compute the quantity ##EQU4## Thisquantity, along with θ_(C) ref itself and σ are provided as inputs tosummer 4303, which computes ##EQU5## and provides this quantity as theθ_(PC) ref input to cluster block 4301. The cluster block 4301 isconfigured as in FIG. 34, except that θ_(PC) ref is no longer fixed atπ, but varies as just described. The balancing block 4304 is configuredas in FIG. 33, but the joystick gains K10 and K11 are set to 0. Thesummer 4305 provides compensation to the pitch reading of theinclinometer in the same manner as described above in connection withFIG. 35, and the output of summer 4305 is differentiated bydifferentiator 4306 to provide correction of θ_(I) in the mannerdescribed above in connection with FIG. 35, so corrected pitch inputs θand θ are provided to the wheel balancing algorithm 4304. The inputsrθ_(wl) and rθ_(wr) to balancing block are also derived in the samemanner as described above in connection with FIG. 35.

FIGS. 40A and 40B illustrate orientation of the cluster in the resetangle origins sequence. In this step, the system changes the identity ofthe "leg" (referred to in item 2 of the conventions discussed afterTable 1), for the purpose measuring state variables, from thatassociated with the lower wheel to that associated with the wheel on thenext stair. As a result, since there are three wheels in the cluster,and the total angular distance around the cluster's center is 2πradians, this step adds 2π/3 radians to θ_(PC) and subtracts 2π/3radians from θ_(C). There is no motion associated with this step.

FIGS. 41A and 41B illustrate orientation of the cluster in the transferweight sequence. In this sequence, the weight of the vehicle and of thesubject is transferred from the wheel on the lower stair to the wheel onthe upper stair. It is here implemented as a pre-programmed operationbased on the known geometry of the stairs and the cluster. The value ofθ_(C) does not change during this sequence. The value of θ_(PC) mustchange to reflect the new location of the vehicle's center of mass. Toachieve this result, an input of θ_(PC) ref as a function of time isprovided on line 3413 to the cluster block shown in FIG. 34 and to thewheel block of FIG.44. Because this sequence is programmed, the climbblock of FIG. 45 and the wheel balance block of FIG. 33 are not active.In FIG. 44, the θ_(PC) ref input is run through divider 441 and thenprovided to summers 443 and 442 that provide control signals, via PIDcontrol loops 445 and 444 and saturation limits 447 and 446, to the leftand right motor wheels respectively. The summers 443 and 442 alsosubtract the values of θ_(PWl) and θ_(PWr) derived by running theangular velocity information from left and right wheel encoders throughintegrators 448 and 449 respectively.

FIGS. 42A, 42B, and 42C illustrate orientation of the cluster in theclimb sequence. In this sequence, the wheel of the vehicle is rotated ina forward direction toward the next stair riser while simultaneouslyrotating the cluster to position the next balancing wheel on the nextstair tread. The cluster rotation θ_(C) is proportional to the distancetraveled by the wheel on the stair tread. In this sequence, there is noreference position input. The subject leans or pulls on the hand rail inorder to cause the vehicle to move forward. The cluster rotatesautomatically as a result of the feedback from θ_(W) to θ_(C) over path451 in FIG. 45. At the beginning of the climb sequence, x is set to 0.The control algorithm in this sequence needs to monitor either θc_(C) orθ_(PC) and move to the transfer weight sequence when this angle reachesits final value. On the last stair, instead of stopping at the finishingangles shown in FIG. 42C, the process must be stopped at θ_(C) =0 orθ_(PC) =π. Then the vehicle should return to normal balancing mode. Thebalancing block 453 and the cluster block 452 are as described above inconnection with FIGS. 33 and 34 respectively. The derivation of inputsθ, θ, rθ_(wl) and rθ_(wr) to the balancing block 453 is as describedabove in connection with FIGS. 43 and 35. Indeed, the configuration ofFIG. 45 is substantially similar to that of FIG. 43, with the singulardifference that θ_(C) ref is no longer independently varied, but insteadis made a function of θ_(W), which is derived by taking the average, viasummer 454 and divider 455, of θ_(Wl) and θ_(Wr) Accordingly, the θ_(W)value on line 451 is run through processor 456 to determine the quantity##EQU6## which causes the correct amount of cluster rotation in relationto wheel rotation for the stair geometry and is provided as an input tosummer 457 along with the initial value of θ_(C), namely θ_(C) st. Theoutput of summer 457 is θ_(C) ref.

Although the FIGS. 33-45 show analog control algorithms, they have beenimplemented in a number of embodiments using microprocessor programmeddigital control. However, it is wholly within the scope of the presentinvention to use direct analog controls as well as a hybrid of analogand digital controls. Analog controls have been successfullyimplemented, for example, in a version of the vehicle of FIG. 21, usinga pair of laterally disposed wheels in lieu of clusters.

Speed Limiting

In a further embodiment, any of the foregoing embodiments of a vehiclein accordance with the present invention may be provided with speedlimiting to maintain balance and control, which may otherwise be lost ifthe wheels (or arcuate elements) were permitted to reach the maximumspeed of which they are currently capable of being driven.

Speed limiting is accomplished by pitching the vehicle back in thedirection opposite from the current direction of travel, which causesthe vehicle to slow down. In this embodiment, the vehicle is pitchedback by adding a pitch modification to the inclinometer pitch value.Speed limiting occurs whenever the vehicle velocity of the vehicleexceeds a threshold that is the determined speed limit of the vehicle.The pitch modification is determined by looking at the differencebetween the vehicle velocity and the determined speed limit, integratedover time. The pitch modification sequence is maintained until thevehicle slows to the desired dropout speed (some speed slightly belowthe speed limit), and then the pitch angle is smoothly returned to itsoriginal value.

One method for determining the speed limit of the vehicle is to monitorthe battery voltage, which is then used to estimate the maximum velocitythe vehicle is currently capable of maintaining. Another method is tomeasure the voltages of the battery and the motor and to monitor thedifference between the two; the difference provides an estimate of theamount of velocity margin currently available to the vehicle.

Use of Sensors in Stair-Climbing

As described in connection with FIG. 37 above, stair climbing and otherobstacle traversal may be effectuated utilizing a lean mode, and theclimb ratio may be selected manually or automatically. This sectiondescribes how sensors may be utilized in a further embodiment to achieveautomatic adjustment of the climb ratio. In the lean mode, clusters arethe "masters" and wheels are "slaves." The climb ratio expresses theratio between cluster rotation and wheel rotation. For example:

i) A climb ratio of zero means that the wheels do not move at all whenthe clusters move.

ii) A climb ratio of 0.25 means that the wheel makes 1/4 rotation in thesame direction as the cluster for each cluster rotation.

iii) A climb ratio of -0.5 means that the wheel makes 1/2 rotation inthe direction opposite to the cluster for each cluster rotation.

Referring now to FIGS. 46 and 47, there is shown a vehicle having anarrangement such as a chair 461 for supporting a human subject. Thechair 461 has associated with it a ground-contacting module in the formof a pair of clusters 462, each motor-driven and each having a plurality(here three) of wheels 463. The wheel set of each cluster is alsomotor-driven. The clusters 462 are linked in this case by a tube inwhich may be housed the cluster motors. The clusters 462 are part of anassembly that includes the chair 461, which is mounted to the clustertube via thigh and calf linkages 466 and 464 respectively andmotor-driven hip and knee joints 467 and 465 respectively. The hip,knee, and cluster drives function in concert to affect a height changeof the seat 461. Note that the cluster drive is acting as an ankle inthis case, as it rotates the calf about the cluster. The clusterattitude is maintained by the balancing algorithm. The vehicle of thisembodiment is provided with a sensor A, looking in a forward directionalong path 468 and mounted just above the cluster tube, far enough abovelevel ground to sense the riser of the second step of stairs 460 to beclimbed. (Note that if a curb is being climbed, no riser would besensed.) Sensor A is used only when ascending stairs. The vehicle ofthis embodiment is also provided with sensor B, looking in a downwarddirection along path 469 and mounted to the cluster tube. It senses thedistance from its face to the ground below. It is placed in front of thetube, far enough above level ground to sense the tread of the step aboutto be climbed. Sensors A and B may be of any type known in the art,including ultrasonic, for sensing distance.

As shown in FIG. 47, when the vehicle is descending, sensor B senses theend of the step that the device is currently on, by detecting the changein height. Sensor C is mounted to the footrest of chair 461, and looksin a downward direction along path 471. It senses the distance from itsface to the ground below. This sensor is only used when descending. Itis placed far enough above ground and far enough ahead of the clustertube to see the edge of the upper landing when preparing to descend.

In this embodiment, to ascend stairs, the driver of the vehicle issues a"climb up" command via the driver's interface while in balance mode. Theseat is then automatically raised to full height, allowing the driver'sfeet to clear the steps in front of the driver. The vehicle is thendriven towards the stairs. When sensor B senses a step (as a change indistance from the sensor to the ground), the vehicle enters lean mode,causing it to "fall" onto the first step (two wheels on the lowerlanding, two on the first step). Once the vehicle is in lean mode, thecenter-of-gravity (CG) is automatically shifted forward. This shiftmakes it easier for the driver to lean forward. The driver leans forwardto create a pitch error. As a result, the cluster balancing algorithmapplies a torque to the cluster motors. This torque rotates the clustersand causes the device to ascend the stair.

An algorithm is employed to adjust dynamically the climb ratio at theinstant the transition is made from four wheels on two steps to twowheels on one step. This pertinent instant is determined not by asensor, but by looking for the following information to be true:

i) the vehicle was told to ascend,

ii) shift is done,

iii) clusters have made 2π/3 rotations since the last climb ratioadjustment,

iv) cluster position is within a certain window,

v) the cluster torque command was below a certain threshold and thederivative of the command was negative (corresponding to setting wheelsdown on the step), and

vi) the cluster torque command is above a certain threshold and thederivative of the command is positive (corresponding to lifting wheelsoff the step).

At the pertinent instant above, the algorithm uses sensor A to determinethe distance to the next step, the fact that it will take 2π/3 rotationsof the cluster to get to the next step, and the wheel radius tocalculate the climb ratio. If sensor A reads out-of-range (no riser,ready to step onto a landing), or a distance beyond a certain threshold(too far to riser, must go to balance mode first), it is noted that thisis the last step; then the control goes to last step processing. Thisprocedure is repeated for each successive step until the last step.

At the last step, the CG is shifted back to center, and the height islowered. Although this makes it more difficult to lean-up the last step,it makes the vehicle more stable once on the landing. A large climbratio is selected to push the vehicle well onto the landing for thetransition to balance mode. The driver again leans forward. When it isdetermined that a zero crossing (defined above in connection with FIG.38) has occurred, the vehicle switches to balance mode. It is nowbalancing on the upper landing using its wheels.

Descent is handled in a manner analogous to ascent. The driver issues a"climb down" command via the driver's interface while in balance mode.The seat is automatically lowered to minimum height (if not alreadythere). This is primarily to increase the feeling of security in thedriver. Sensor C is quite far out front of the wheels, so that thevehicle does not need to be too close to the edge of the step while inbalance mode. Since the vehicle will be so far from the edge when leanmode is entered, the climb ratio is adjusted to a fairly high value.This allows the vehicle to reach the edge of the step once lean mode isentered. When sensor C senses a step (as a change in distance to theground), the vehicle enters lean mode. Once in lean mode, thecenter-of-gravity (CG) is shifted rearward. This shift makes it easierfor the driver to lean back to control descent. To descend, the driverfirst leans forward to create a pitch error, causing the vehicle todescend the stairs. Approximately half-way through the rotation, thedriver must lean back slightly to slow the descent onto the next stair.The climb ratio is adjusted by using down-looking sensor B to sense theend of the step the wheels are currently on. The climb ratio is adjustedto a large positive value when no edge is sensed (cluster command signalpositive, climb ratio either negative or nominal, and sensor B below acertain threshold). The large positive climb ratio causes relativelyrapid rolling of the wheels, so that the vehicle soon reaches the edgeof the current step. This action establishing the large positive climbratio will be overridden, however, if it causes the vehicle to get tooclose to the edge:

i) The climb ratio is set to a nominal positive value when sensor Bsenses the edge (distance greater than a specified threshold and theclimb ratio is positive). Once this value is set, it should suffice toget the vehicle into the proper position.

ii) The climb ratio is adjusted to a small negative value if it isdetermined that the vehicle is too close to the edge (cluster signalpositive, climb ratio either negative or nominal, and sensor B above acertain threshold). The negative climb ratio rolls the wheels back asthe cluster rotates, keeping the vehicle safely on the current step.

The descent pattern is repeated for each step. Once the vehicle reachesthe landing at the bottom of the stairs, both sensors B and C sense nomore steps (sensor readings below certain thresholds). When this occurs,the vehicle transfers to the balance mode.

Mode Transitions

Although transitions between lean mode and balance mode of the vehicleof FIGS. 46 and 47 may be managed as described in connection with FIG.38, in a further embodiment of a vehicle in accordance with the presentinvention, the transition between modes may be managed on a more activeand continuous basis. This embodiment utilizes joints 465 and 467 tocontrol height of seat 461 and joint 467 in particular to control tiltof the seat 461. In lean mode, the vehicle has four wheels on the ground(two on the ground from each cluster) so that it may climb stairs ormove over obstacles. The cluster motor output is adjusted according tothe inclinometer pitch and pitch rate, and cluster encoder velocity.Transition to balance mode occurs when the Lean/Balance switch ispressed.

In transition to balance mode, the center of gravity is shifted over thefront ground-contacting wheel of each cluster. To accomplish this, anartificial pitch error is created by gradually increasing an offsetadded to the inclinometer reading. This artificial pitch error causesthe cluster balancing algorithm to apply a torque to the cluster motors,causing rotation of the clusters. This torque pitches the seat forward,moving the seat over the front wheels, in proportion to the artificialpitch error. (Simultaneously, the same offset may be used to command anew desired position in the seat tilt, determined by joint 467 of FIG.46, thereby keeping the seat level.) When the cluster position isgreater than the prescribed cluster transition angle (which may be basedupon the amount of CG shift), the transition velocity of the cluster isinitialized to the speed at which the cluster is currently moving, andbalance mode is entered.

At the time balance mode is entered, the clusters have been rotated onlypartially, and the rear pair of wheels are typically about 2-5 cm abovethe ground. When entering balance mode, each of the clusters must berotated from its current position until its "leg" (as defined in item 2following Table 1) and "post" (also as defined in item 2) are verticalas in FIG. 46. This is accomplished by rotating the cluster at aprescribed velocity, gradually adjusted from the initialized transitionvelocity of the cluster. In this manner, cluster rotation continuessmoothly on entry into the balance mode until the cluster reaches itstarget position. During this cluster rotation, the artificial pitcherror is reduced to keep the CG over the ground contacting elementsuntil it is entirely removed from the inclinometer reading. If this werenot done, the device would translate (in balance mode) because of theartificial pitch error.

Cluster position may be used to command seat tilt, thereby keeping theseat level as the seat post moves rearward. Once the cluster leg andpost are vertical (dusters have stopped rotating) and the seat is level,the transition to balance mode from lean mode is complete.

If the Lean/Balance switch is pressed when the vehicle is in balancemode, transition to lean mode is entered. The desired cluster positionis gradually changed from the initial position (where the cluster legand post are vertical) to a final desired position (where the front pairof wheels are at a prescribed distance above the ground).Simultaneously, an artificial pitch error is introduced to keep the CGover the balancing wheels. Again, cluster position may be used tocommand seat tilt, thereby keeping the seat level as the seat post movesrearward.

Once the cluster has rotated to a position where the second pair ofwheels are within a prescribed distance above the ground, lean mode isentered, causing the device to drop onto four wheels. Once the vehicleis in lean mode, the artificial pitch error that kept the cluster postpitched rearward and the seat tilted forward is promptly, but smoothly,removed. As a result, the applied cluster torque causes the cluster postto rotate forward to its vertical position. Simultaneously, the torquemay be applied to the seat tilt to keep the seat level. Once the clusterpost is vertical and the seat level, the transition from balance mode tolean mode is complete.

Configuration Using Harmonic Drives

In a further embodiment of the invention, the embodiment of FIGS. 46 and47 has been realized mechanically in a configuration, similar that ofFIGS. 9-12, utilizing harmonic drives. This configuration is shown inFIGS. 48-52.

FIG. 48 is a partially cut away vertical section viewed from the frontshowing the overall mechanical layout of the vehicle of this embodiment.In this view can be seen, among other things, the seat frame 481, thehip assembly 482, the thigh linkage 483, the knee assembly 484, the calflinkage 486, and the wheels 485.

FIG. 49 is an expanded view of a part of FIG. 48, showing mechanicaldetails of the cluster portion of the vehicle. Wheel motors 4913 on leftand right sides drive the wheels 485 on left and right sidesrespectively; the wheels on any given side are powered synchronously.The wheels are driven via a two-stage reduction. In the first stage, themotor 4913 turns wheel drive pulley 496 to move timing belt 495. In thesecond stage are employed three sets 4911 of herringbone gears, one foreach wheel, to drive the wheel drive shaft 4912. The side of each of themotors 4913 that is not coupled to the wheel drive pulley is coupled toa shaft encoder 4914. Both clusters in this embodiment are driven by thesame motor 4924 via a three-stage reduction. In the first stage, themotor 4924 turns cluster drive pulley 4921. The pulley 4921 causesmotion of a timing belt. The timing belt is best seen as item 501 inFIG. 50, which shows detail of the cluster drive arrangement. The timingbelt 501 drives a second stage of helical gears, including first gear502 and second gear 4922. The second gear 4922 drives a pair ofintermediate shafts 493, which drive a final set 494 of helical gears ateach cluster. The side of the cluster motor 4924 that is not coupled tothe cluster drive pulley 4921 is coupled to a shaft encoder 4925. Thefar side of the shaft turning the cluster drive pulley 4921 is coupledto cluster brake assembly 4926, which may be used to lock the clustersin position when the vehicle is parked or in the balance mode. Thehousings of the two wheel motors 4913 and the cluster motor 4924 arebolted together to form a tube, which provides the structure joining thecluster assemblies. The calf 486 is rigidly affixed to this structure.

FIG. 51 shows an end view of a cluster. The single timing belt 495 ofFIG. 49 is shown driven by wheel drive pulley 496 in the center of thecluster. The timing belt 495 drives a larger pulley 511 on each of thethree legs. This larger pulley 511 drives a gear set including piniongear 512 and output gear 513 which drives the wheel 485. The four idlerpulleys 514 keep the belt 49 from interfering with the cluster housing515 and also provide maximum wrap angle around the drive pulley.

FIG. 52 shows the mechanical details of the hip and knee joints. Bothjoints are mechanically identical. The motor magnet rotor 5211, acted onby stator 5212, turns a shaft 5213, mounted in bearings 522 and 5272.The shaft 5213 rotates the wave generator 5271, which is anapproximately elliptically shaped piece, rotating within bearing 5272.The wave generator 5271 causes the harmonic drive cup 5262 toincrementally engage and disengage its teeth with the harmonic drivespline 5261. This process causes the thigh 483 to move with respect tothe calf 486 or seat frame 481 with a very high reduction ratio. Anelectromagnetic power off brake having electromagnet 5281 and brake pad5282 can be applied to the wave generator 5271 to prevent the joint fromrotating. This allows the motor to be turned off when the joint is notbeing actuated. A potentiometer 524 is geared through gear train 5241 tothe harmonic drive cup 5262 to give absolute position feedback, while anencoder (not shown) is fixed to the motor shaft at position 523 toprovide incremental position information.

Multiple Processors

Although the embodiment of FIG. 27 shows use of a single microcontroller board 272, we have found it advantageous in some embodimentsto utilize a number of microprocessors operating in parallel. In afurther embodiment, for example, applicable to the mechanical designdiscussed in connection with FIGS. 48-52, there are employed fourdifferent microprocessors operating in parallel, each of which postsmessages to a communications bus, allowing the microprocessors tomonitor each other. There is also a technician's interface (TI) whichallows the technician to change gains, reprogram the processor etc. Thefour different microprocessors control the different components of thesystem as follows: microprocessor 1 controls the button, the knee andhip, and the joystick (x and y axes); microprocessor 2 controls distancemeasurement, presence checking (for a person), battery monitoring, anduser interface (thereby controlling modes of the vehicle);microprocessor 3 controls the cluster balancing algorithm;microprocessor 4 controls wheel balancing algorithms. Additionalprocessors may be desirably employed, depending on the complexity of thedistance measurement and other issues. This will not necessarily limitthe number of processors.

The advantages of the parallel processing realized by this embodimentare: safety (each microprocessor operates independently, so that failureof one microprocessor will not mean failure of all functions); abilityto more easily develop redundant systems; reduced power requirements(multiple less powerful microprocessors which together are as powerfulas a PC); and simultaneous operations (multiple slower microprocessorscan operate at the same processing speed as the PC).

Further embodiments

The present invention may also be implemented in a number of furtherembodiments. We have found that a vehicle in accordance with theinvention may act suitably as a prosthetic device for persons who havean impairment, caused by disease (such as Parkinson's Disease or eardisorders) or defect, in their ability to maintain balance or to achievelocomotion. The prosthetic device achieved by the vehicle functions asan extension of the person's own balance system and locomotion system,since the vehicle has a feedback loop that takes into account changes inthe vehicle's center of gravity attributable to motion of the personrelative to the vehicle. Providing a vehicle to such a handicappedperson is thus a method of fitting a prosthesis that permits locomotionand balance control when these would otherwise be unavailable. We haveobserved a dramatic restoration of balance and locomotion control to aperson suffering from Parkinson's Disease who utilized a vehicle inaccordance with embodiments of the present invention.

Given the complex contributions from the human driver in utilizingvarious embodiments of the vehicle of the present invention to achievelocomotion over varied conditions, it is not surprising that visualorientation and displacement information is typically of greatimportance in general and in utilization of these embodiments.Nevertheless, there may be circumstances when the visual information iseither impaired (owing to darkness or disability) or insufficient. In afurther embodiment of the present invention, the vehicle is providedwith one or more non-visual outputs to indicate orientation or directionand velocity. Such outputs may be tactile, for example, or sonic; theoutputs are modulated by a modulator to reflect the vehicle's speed andorientation. Shown in FIG. 53, fore example, is the case of a sonicoutput generated by generator 531, and modulated by modulator 532 havingorientation and speed inputs 533 and 534 respectively. In this case, arepeated tone may be employed: the rate of repetition of the tone may beused to indicate speed and the pitch of the tone may be used to indicatedirection of motion and orientation (forward, for example, with a higherpitch; backward with a lower pitch; upright with a center pitch), andthe degree of change in pitch indicative of the extent of lean, i.e.,vehicle pitch angle (with the effect that here sound pitch is equatedwith vehicle pitch).

What is claimed is:
 1. A vehicle, for transporting a human subject overa surface that may be irregular, the vehicle comprising:(a) a supportfor supporting the subject, the support having left and right sides anddefining fore-aft and lateral planes; (b) a ground-contacting module,including a pair of ground-contacting members, laterally disposed withrespect to one another, movably attached to the support, for suspendingthe subject in the support over the surface, the support and theground-contacting module being components of an assembly; (c) amotorized drive arrangement, mounted to the assembly for causinglocomotion of the assembly and the subject over the surface; and (d) acontrol loop, in which the motorized drive is included, for dynamicallymaintaining stability in the fore-aft plane by operation of themotorized drive arrangement so that the net torque experienced by theassembly about the point of contact with the surface, taking intoaccount torques caused by gravity as well as by all other externalforces and by the motorized drive, causes a desired acceleration andsustained locomotion of the assembly, such stability being maintainedeven while the assembly experiences varying forces andaccelerations;wherein the control loop is configured so that fore andaft sustained motion of the vehicle is controlled by fore and aftleaning of the vehicle caused by the subject, and in maintainingstability in the fore-aft plane the control loop does not cancel outsuch leaning under normal conditions of locomotion.
 2. A vehicleaccording to claim 1, wherein each ground-contacting member includes awheel, the vehicle further comprising:wheel control means forcontrolling the rotation of each of the wheels separately, the wheelcontrol means having a balance mode, utilizing the control loop, inwhich the wheels are driven in such a manner as to maintain balance ofthe vehicle in the fore-aft plane.
 3. A vehicle according to claim 1,wherein each ground-contacting member includes a cluster of wheels forcontacting the ground, each cluster being rotatably mounted on andmotor-driven about a laterally disposed central axis, and each of thewheels in each cluster being rotatably mounted about an axis parallel tothe central axis, the wheels being capable of being motor-drivenindependently of the cluster.
 4. A vehicle according to claim 3, whereinthe central axes of the clusters are so disposed as to be substantiallycoincident with one another.
 5. A vehicle according to claim 4, whereinthe distance from the central axis through a diameter of each wheel isapproximately the same for each of the wheels in the cluster.
 6. Avehicle according to claim 4, wherein each cluster has two wheels ofsubstantially equal diameter.
 7. A vehicle according to claim 4, whereineach cluster has three wheels of substantially equal diameter.
 8. Avehicle according to claim 4, further comprising:cluster control meansfor controlling the angular orientation of each cluster about thecentral axis; and wheel control means for controlling separately, as tothe wheels of each cluster, the rotation of wheels in contact with theground.
 9. A vehicle according to claim 8, wherein the wheel controlmeans has a balance mode, utilizing the control loop, in which thewheels of each cluster in contact with the ground are driven in such amanner as to maintain balance of the vehicle in the fore-aft plane. 10.A vehicle according to claim 8, wherein the wheel control means has aslave mode in which the wheels are driven as a function of the rotationof the dusters; and the cluster control means has a lean mode, utilizingthe control loop, in which the clusters are driven in such a manner asto tend to maintain balance of the vehicle in the fore-aft plane whilethe wheels are in the slave mode, so as to permit the vehicle to ascendor descend stairs or other surface features.
 11. A vehicle according toclaim 10, wherein the wheel control means has a balance mode, utilizingthe control loop, in which the wheels of each cluster in contact withthe ground are driven in such a manner as to maintain balance of thevehicle in the fore-aft plane.
 12. A vehicle according to claim 11,wherein the wheel control means has a wheel transition mode, used in thetransition from the slave mode to the balance mode, operative to prevententering the balance mode until a zero crossing by the clusters has beensensed.
 13. A vehicle according to claim 8, furthercomprising:coordination control means for coordinating operation of thecluster control means with that of the wheel control means, thecoordination control means having a stair climbing mode to cause stepsas follows:(1) start, in which the assembly, balanced on a first wheelpair, one from each cluster, is disposed adjacent to a stair and theclusters are then rotated so that a second wheel pair is resting on thestair; (2) transfer weight, in which the weight of the vehicle and thesubject is transferred from the lower first wheel pair to the secondwheel pair on the stair by motion of the clusters relative to theassembly while the wheels are driven to maintain the position of theclusters relative to the world; (3) climb, in which the second wheelpair is driven to move the vehicle forward to the riser of thesucceeding stair while simultaneously the clusters are driven toposition the next wheel pair on the tread of the succeeding stair, thisstep being carried out while the wheel control means is in the balancemode; and wherein steps (2) and (3) are alternated until the last stair,at which point normal balance mode of the wheel control means is enteredinto.
 14. A vehicle according to claim 10, further comprising:slavefunction adjustment for modifying the function in the slave mode, sothat the vehicle may accommodate climbing and descent of stairs and ofother surface features having varying geometries.
 15. A vehicleaccording to claim 14, the vehicle further comprising:sensingarrangement for sensing the physical relation of the vehicle to surfacefeatures, the sensing arrangement in communication with the slavefunction adjustment, so that stairs and other surface features may benegotiated automatically by the vehicle.
 16. A vehicle according toclaim 4, further comprising:a joystick for use by the subject incontrolling direction of the vehicle.
 17. A vehicle according to claim4, further comprising:leaning means for sensing leaning of the vehiclein a given direction that may include components in any, or both, of thefore-aft and lateral planes, and for controlling the motorized drive tocause the vehicle to move in the direction in which the vehicle maylean.
 18. A vehicle according to claim 17, wherein the leaning meansincludes a force plate.
 19. A vehicle according to claim 17, wherein theleaning means includes a proximity sensor.
 20. A vehicle according toclaim 4, wherein the support includes a chair having a seat, hingedlyattached to the assembly, so as to have a first position in which thesubject may be seated on the seat and a second position in which thesubject may stand.
 21. A vehicle according to claim 4, wherein thevehicle has a roll axis and a pitch axis, further comprising:attitudedetermination means for determining the attitude of the support;attitude control means for controlling the attitude of the supportrelative to the ground-contacting member.
 22. A vehicle according toclaim 21, further comprising:roll adjustment means for permittingadjustment of the angular orientation of the support with respect to theground-contacting module about an axis approximately parallel to theroll axis of the vehicle, the roll adjustment means controlled by theattitude control means.
 23. A vehicle according to claim 22, furthercomprising:banking means for causing the roll adjustment means, in thecourse of a turn, to bank the support in the general direction ofturning.
 24. A vehicle according to claim 21, further comprising:tiltadjustment means for permitting adjustment of the angular orientation ofthe support with respect to the ground-contacting module about an axisapproximately parallel to the pitch axis of the vehicle, the tiltadjustment means controlled by the attitude control means.
 25. A vehicleaccording to claim 4, further comprising:height adjustment means foradjusting the height of the support relative to the ground.
 26. Avehicle according to claim 25, wherein the height adjustment meansincludes a variable extension between the support and theground-contacting module.
 27. A vehicle according to claim 4, whereinthe support has a base surface for supporting the subject and whereinthe clusters are movably attached to the support in such a manner thatthe distance between the point of contact of each cluster with theground and the base surface is sufficiently small as to permit a personto step from the ground onto the support.
 28. A vehicle according toclaim 27, further comprising a handle, affixed to the support, having agrip at approximately waist height of the subject.
 29. A vehicleaccording to claim 28, further comprising:a joystick, mounted on thehandle, for use by the subject in controlling direction of the vehicle.30. A vehicle according to claim 27, further comprising:leaning meansfor sensing leaning of the subject in a given direction and forcontrolling the motorized drive to cause the vehicle to move in thedirection in which the subject may lean.
 31. A vehicle according toclaim 27, further comprising:leaning means for sensing leaning of thesubject in a given direction that may include components in any, orboth, of the fore-aft and lateral planes, and for controlling themotorized drive to cause the vehicle to move in the direction in whichthe subject may lean.
 32. A vehicle according to claim 1, wherein eachground-contacting member includes a plurality of axially adjacent androtatably mounted arcuate element groups, the arcuate elements of eachgroup being mounted to a support member, each support member beingrotatably mounted and motor-driven about a central axis.
 33. A vehicleaccording to claim 32, wherein the radially outermost extent of eacharcuate element has a generally constant main radius of curvatureconforming generally with that of a circle having a radius equal to suchextent.
 34. A vehicle according to claim 33, wherein each arcuateelement has a leading portion and a trailing portion determined inrelation to forward motion of the assembly, the leading portioncontacting the ground first during forward motion, each portion having atip, and wherein the radius of curvature of the arcuate element near thetip of each leading portion is somewhat smaller than the element's mainradius of curvature.
 35. A vehicle according to claim 33, wherein eacharcuate element has a leading portion and a trailing portion determinedin relation to forward motion of the assembly, the leading portioncontacting the ground first during forward motion, each portion having atip, and wherein the radius of curvature of each arcuate element nearthe tip of its trailing portion is somewhat smaller than such element'smain radius of curvature.
 36. A vehicle according to claim 33, whereineach arcuate element has a leading portion and a trailing portiondetermined in relation to forward motion of the assembly, the leadingportion contacting the ground first during forward motion, each portionhaving a tip, and wherein the radius of curvature of each arcuateelement near at least one of its tips differs from the main radius ofcurvature.
 37. A vehicle according to claim 33, wherein each arcuateelement has a leading portion and a trailing portion determined inrelation to forward motion of the assembly, the leading portioncontacting the ground first during forward motion, each portion having atip, and wherein at least one of the tips of each arcuate element isdeflectably mounted and is coupled to a deflection arrangement, so thaton actuation the local radius of curvature may be modified.
 38. Avehicle according to claim 32, wherein the support is proximate to theground to permit a subject to stand thereon.
 39. A vehicle according toclaim 38, further comprising a handle, affixed to the support, having agrip at approximately waist height of the subject.
 40. A vehicleaccording to claim 39, further comprising:a joystick, mounted on thehandle, for use by the subject in controlling direction of the vehicle.41. A vehicle according to claim 32, further comprising:drive controlmeans, including the control loop, for driving the support members in afirst mode wherein a first arcuate element in each group of axiallyadjacent arcuate elements generally remains in contact with the groundup to a point near in arcuate distance to where the next succeedingarcuate element comes in contact with the ground, and so on assuccessive arcuate elements come in contact with the ground, so as toprovide substantially continuous rolling motion of the vehicle along thearcuate elements.
 42. A vehicle according to claim 41, wherein the drivecontrol means includes means for driving the support members in a secondmode to permit ascent and descent of stairs and other surface features.43. A vehicle according to claim 42, further comprising: means forcausing a second one of the arcuate elements of each group to land on asucceeding surface feature, which may include a step, when a first oneof the elements of each group is on a preceding surface feature.
 44. Avehicle according to claim 1, wherein the support has a base surface forsupporting the subject and wherein the ground-contacting members aremovably attached to the support in such a manner that the distancebetween the point of contact of each ground-contacting member with theground and the base surface is sufficiently small as to permit a personto step from the ground onto the support.
 45. A vehicle according toclaim 44, further comprising:a handle, affixed to the support, having agrip at approximately waist height of the subject.
 46. A vehicleaccording to claim 44, wherein the ground-contacting members are wheels.47. A vehicle according to claim 45 further comprising:a joystick,mounted on the handle, for use by the subject in controlling directionof the vehicle.
 48. A vehicle according to claim 44, furthercomprising:leaning means for sensing leaning of the vehicle in a givendirection and for controlling the motorized drive to cause the vehicleto move in the direction in which the vehicle may lean.
 49. A vehiclefor transporting a human subject over ground, the vehicle comprising:(a)a support, having a base surface, for supporting the subject in astanding position, the support having left and right sides and definingfore-aft and lateral planes; (b) a pair of ground-contacting members,laterally disposed with respect to one another and movably attached tothe support in such a manner that the distance between the point ofcontact of each ground-contacting member with the ground and the basesurface is sufficiently small as to permit a person to step from theground onto the support, each ground-contacting member includes acluster of wheels for contacting the ground, each cluster beingrotatably mounted on and motor-driven about a laterally disposed centralaxis, and each of the wheels in each cluster being rotatably mountedabout an axis parallel to the central axis, the wheels being capable ofbeing motor-driven independently of the cluster, the members and thesupport being components of an assembly; (c) a motorized drivearrangement, mounted to the assembly for causing locomotion of theassembly and the subject over the surface; and (d) a control loop, inwhich the motorized drive is included, for dynamically maintainingstability in the fore-aft plane by operation of the motorized drivearrangement so that the net torque experienced by the assembly about thepoint of contact with the surface, taking into account torques caused bygravity as well as by all other external forces and by the motorizeddrive, causes a desired acceleration and sustained locomotion of theassembly, such stability being maintained even while the assemblyexperiences varying forces and accelerations.
 50. A vehicle according toclaim 49, wherein the control loop is configured so that fore and aftmotion of the vehicle is controlled by fore and aft leaning of thevehicle as affected by the subject.
 51. A vehicle, for transporting ahuman subject over a surface that may be irregular, the vehiclecomprising:(a) a support for supporting the subject, the support havingleft and right sides and defining fore-aft and lateral planes; (b) aground-contacting module for suspending the subject in the support overthe surface, the support and the ground-contacting module beingcomponents of an assembly; (c) a motorized drive arrangement, mounted tothe assembly for causing locomotion of the assembly and the subject overthe surface; (d) a control loop, in which the motorized drivearrangement is included, for dynamically maintaining stability in thefore-aft plane by operation of the motorized drive arrangement so thatthe net torque experienced by the assembly about the point of contactwith the surface, taking into account torques caused by gravity and byall other external forces and by the motorized drive, causes a desiredacceleration and sustained locomotion of the assembly, such stabilitybeing maintained even while the assembly experiences varying forces andaccelerations;wherein the control loop is configured so that fore andaft sustained motion of the vehicle is controlled by fore and aftleaning of the vehicle caused by the subject, and in maintainingstability in the fore-aft plane the control loop does not cancel outsuch leaning under normal conditions of locomotion.